[atul]

Agarthan mages have earth and summon earth power gives reinvigoration 4 as an extra bonus, so I'd think reinvigoration bless isn't that important. Does it stack, on the other hand? 50 turns of Magma Bolts!

Bless on MA Agartha overall isn't probably that big a deal since their recruitable sacred troops are capital-only and actually going up the Enchantment route (sacred statues) isn't that fast a strategy. By the time you're ench4 thau2 (for gems and decent statues) you could nearly have researched conj3 for earth power and gone either alt2 for earth meld or evocation tree, thus making the earth readers a power to be reckoned with. Taking mages to battle or putting them into summoning spree both prevent them from researching, anyway.

Edit: Max, on the other hand, MA Agartha has holy3 mages, so one casting of battlefield-wide blessing isn't that big a hassle. But, what I wrote previously still applies, somewhat.